Weber 45 MCHH

I am new to this site but recently had some headaches with the Weber 45 MCHH carburetor on a stock 77' B that I have learned from and I hope to help others.

Long story short, the set screw that holds the venturi in position backed out and found itself a new home on some highway. The allowed the venturi to "spin" and not allow mainjet fuel into the intake appropriately. This ultimately resulted in it running lean at anything over about 1500-2000 RPM. After much headache and much less hair this was figured out and "repaired". Upon trying to test drive the car it still ran terribly. Come to find out I had put the Venturi in backwards, reversing it fixed all of the issues. Unfortunately there is little info out there on the 45 MCHH. It took me a few days on the internet just trying to find a replacement float. Somehow and somewhere, the check valve for the accelerator pump has disappeared. I replaced it with a "BB" and it seems to work very well. This was done after I was told by three different suppliers that they "can't get those". Hope this helps someone else. I would still like to see an exploded view of the 45 MCHH and some float settings. Everyone says use 45 DCOE settings but if anyone has looked at the 45 MCHH float it is much different than the DCOE and is hard to tell from what portion of the float should the seetings be measured. (The back of the float is at an angle).

Hope this helps,

Get in touch with "Jose" at Weber Direct, 1-866-679-3237, I found him very helpful with any problems I had. As far as float level is concerned, I was told "almost parallel to cover plate" doesn't seem too specific but if you set it up that way all seems well. I also put on a new Carter electronic fuel pump and a Holley fuel regulator and gauge to ensure proper pressure and volume, (pressure 3.5 psi, volume, 70 GPH). I recently installed Pertronix electronic ignition, that made a huge improvement to everything.

Jeremy, give the guys at Pierce Manifolds a call on their tech line if weber direct can't help you. They've good and very helpful. Here's the link and good luck.

http://www.piercemanifolds.com/carbdetails/carburators.htm

I did contact webers direct and unfortunately couldn't get much help. I have spoken to Jose' before and yes, he is very helpful.

I too have placed a Pertronix system in place and it does make a noticeable difference. New fuel pump and pressure regulator have also been installed. The old "B" has never ran better thanks to Mike at Glass Auto Repair in OKC. Alot of difference was made with re-routing some of the vacuum tubing on the manifold. The crankcase is vented to "open air" with a cone type filter attached. The vacuum advance has been completely unhooked. This thing literally purrs. Still have some adjusting to do. It occasionally wants to stall at stop lights. I have fuel pressure regulated down to 2.5.

Thanks,

Jeremy

I have been introduced to Pierce before and sound like a great resource. I will keep them in mind.

Jeremy

I think you'll find that fuel pressure should be 3.5 psi.

By the way, the BB works great as an accelerator pump check valve.

Think outside the box.

Jeremy